Tracking solar collector assembly

ABSTRACT

A tracking solar collector assembly includes Southside supports, North side supports and support structures. Each support structure has pivotal support points defining a tilt axis and supports at least one solar collector. First support points of first and second support structures are pivotally connected to first and second Southside supports. A second support point of the first support structure is pivotally connected to first and second North side supports. A second support point of the second support structure is pivotally connected to second and third North side supports. A tilting assembly causes the solar collector support structures and the solar collectors tilt in unison. A tracking solar collector may comprise a torsion tube rotatable about a torsion tube axis; with the solar panels secured to the torsion tube at an angle with the solar panels located entirely above the torsion tube at noontime.

CROSS-REFERENCE TO OTHER APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/455,649, filed Mar. 18, 2003 and U.S. Provisional Patent ApplicationNo. 60/530,384, filed 17 Dec.

2003. This application is related to U.S. Pat. No. 6,058,930, issued 9May 2000.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

BACKGROUND OF THE INVENTION

This invention relates to solar energy collection, and in particular toan arrangement for driving a number of rows of solar panels to track themotion of the sun relative to the earth. The invention is moreparticularly directed to improvements in efficiency and reliability inthe tracker arrangement for rocking, or rotating, a group or array ofrows of solar panels. The invention applies to solar collectors in whichthe panels are arrays of photovoltaic cells for generating electricalpower, but the same principles can be applied also to arrangements forsolar heating, for example.

Photovoltaic arrays are used for a variety of purposes, including as autility interactive power system, as a power supply for a remote orunmanned site, a cellular phone switch-site power supply, or a villagepower supply. These arrays can have a capacity from a few kilowatts to ahundred kilowatts or more, and can be installed wherever there is areasonably flat area with exposure to the sun for significant portionsof the day.

In general terms, these systems have their photovoltaic panels in theform of rows supported on a torque tube that serves as an axis. Atracker drive system rotates or rocks the rows to keep the panels assquare to the sun as possible. Usually, the rows are arranged with theiraxes disposed in a north-south direction, and the trackers graduallyrotate the rows of panels throughout the day from an east-facingdirection in the morning to a west-facing direction in the afternoon.The rows of panels are brought back to the east-facing orientation forthe next day.

One solar collector arrangement of this type is shown in Barker et al.U.S. Pat. No. 5,228,924. There, each row of panels is affixed to ahorizontal pivot shaft that is supported on two or more support piers onwhich the pivot shaft is journalled. A drive mechanism is mounted on oneof the piers, and pushes against the solar panel at some point that isdisplaced from the shaft. In that case, the drive is of the screw type,and as a drive motor rotates, a shaft retracts or extends to rotate therow of panels in one direction or the other. In this arrangement, eachrow of panels has its own respective drive mechanism, and so these allhave to be synchronized to follow the sun together. With a pier-mounteddrive, it is difficult or impossible to use a single driver to move morethan one row of solar panels.

SUMMARY OF THE INVENTION

One aspect of the invention is directed to tracking solar collectorassembly including first and second Southside supports and first, secondand third north side supports. The Southside supports and the North sidesupports define first and second generally parallel paths. The assemblyalso includes first and second solar collector support structures. Eachsolar collector support structure has first and second spaced apartpivotal support points, the support points defining a tilt axis. Atleast one solar collector is mounted to each solar collector supportstructure. The first support points of the first and second solarcollector support structures are pivotally connected to and supported bythe first and second Southside supports, respectively. The secondsupport point of the first solar collector support structure ispivotally connected to and supported by the first and second North sidesupports. The second support point of the second solar collector supportstructure is pivotally connected to and supported by the second andthird North side supports. The assembly further includes a tiltingassembly. The tilting assembly includes a drive element secured to eachsolar collector support structure; a drive element coupler operablycoupling the drive elements, the drive elements and the drive elementcoupler creating a drive assembly; and a driver coupled to the driveassembly so that operation of the driver causes the drive elements movein unison thus causing the solar collector support structures and thesolar collectors therewith to tilt in unison.

Another aspect of the invention is directed to tracking solar collectorof the type comprising a series of supports oriented on a generallynorth-south axis; a torsion tube, having a torsion tube axis, rotatablymounted to the supports to permit rotation of the torsion tube about thetorsion tube axis; a torsion tube rotator operably coupled to thetorsion tube so to rotate the torsion tube between morning, noontime andevening angular orientations; and solar panels, each having a center ofgravity. The improvement comprises mounting structure securing the solarpanels to the torsion tube at a chosen angle to the torsion tube axiswith each of the solar panels located entirely vertically above thetorsion tube axis when the torsion tube is at the noontime angularorientation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-18 illustrate conventional solar collector and trackerarrangements.

FIGS. 1A, 1B, and 1C are end elevations showing a row of solar panelshaving a conventional pier mounted driver.

FIGS. 2A, 2B, and 2C are end elevations showing a row of solar panelshaving a conventional horizontal ground-supported driver.

FIGS. 3A, 3B, and 3C are end elevations showing a row of solar panelshaving a conventional vertical ground-supported driver.

FIGS. 4A, 4B, and 4C are end elevations of a plurality of rows of solarpanels employing a ground-supported horizontal drive arrangement.

FIG. 5 is a detail view showing the linkage articulation feature.

FIG. 6A is a top view of a horizontal driver and FIG. 6B is a sideelevational view thereof.

FIG. 7 illustrates a plurality of rows of the vertical driver solarpanels configured for uneven terrain.

FIG. 8 illustrates a plurality of rows of the horizontal driver solarpanels configured for uneven terrain.

FIGS. 9A, 9B, and 9C are plan views of arrays of rows of solar panels.

FIG. 10 is an elevation taken at 10-10 in FIG. 9A.

FIGS. 11 and 12 are an end view of a bearing sleeve and a cross sectiontaken at 12-12 of FIG. 11, respectively.

FIGS. 13 and 14 are a cross section and an axial section of the torquetube and pier bearing, showing a coupling between torque tube sections.

FIG. 15 is a simplified side elevational view of a section of the torquetube and the solar panels of FIG. 2A, shown at a noontime or middayorientation and viewed along an east-west orientation, illustrating thedistance between the center of gravity of the solar panel and thetorsion tube axis.

FIG. 16 is a simplified view of the apparatus of FIG. 15 viewed alongthe torsion tube axis.

FIGS. 17 and 18 are similar to FIG. 16 with the structure at arelatively low tilt angle in FIG. 17 and a correspondingly small torquearm X₁, and a relatively large tilt angle in FIG. 18 with a longertorque arm X₂.

FIGS. 19-24 and 25-33 illustrate first and second embodiments of thepresent invention.

FIG. 19 is a simplified representation of a first embodiment of presentinvention, similar to the view of FIG. 15, illustrating mounting a solarpanels to the torsion tube and so that the solar panels are oriented atan angle to the torsion tube axis.

FIGS. 20-22 are views of the invention of FIG. 19 corresponding to FIG.16-18 and illustrating that, due to the tilt angle shown in FIG. 19,torque arms X₁ and X₂ are longer than in the structure shown in FIGS.16-18.

FIG. 23 illustrates a portion of a solar collector and tracking systemmade according to the invention of FIGS. 19-22 with the torque tubesoriented at an angle similar to that shown in FIG. 21.

FIG. 24 is a cross-sectional view of one of the mounting plates takenalong line 24-24 of FIG. 23.

FIG. 25 is a downwardly and North-facing view of the ends of two rows oftracking solar collection assemblies of a second embodiment of theinvention with the PV module arrays of each tracking solar collector ata no-tilt, noontime orientation.

FIG. 26 shows the assembly of FIG. 25 with the PV module arrays tiltedto the West at a West-tilting, afternoon tilt orientation.

FIG. 27 is a side view of a tracking solar collector of FIG. 25.

FIG. 28 is an upwardly and South-East-facing view of a tracking solarcollector of FIG. 25.

FIG. 29 is enlarged view illustrating the tilting assembly, the tiltingassembly including a driver connected to a drive element coupler and adrive element connecting the torque tube to the drive element coupler.FIG. 29 also shows connection of the torque tube to the upper end of thepost of a South side support.

FIG. 29A is a schematic illustration of an alternative to the tiltingassembly of FIG. 29 in which pulley-type drive elements are secured tothe torque tubes and are connected to one another so that rotating onepulley rotates the series of pulleys and the torque tubes therewith.

FIG. 30 is enlarged view of the base of a North side support of FIG. 28.

FIG. 31 is an enlarged view illustrating the connection of the strutsfrom two North side supports to the second support along the torque tubeof FIG. 28.

FIG. 32 is a simplified South-facing view of an alternative to the Northside supports of FIGS. 25-31.

FIG. 33 is a simplified South-facing view of an alternative to the Northside supports of FIG. 32.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

With reference to the Drawing, and initially to FIGS. 1A to 1C, a solartracker array 10 according to the prior art, here is shown from a northaspect. A torque tube 12 serves as a north-south axis, and a row ofsolar panels 14 is attached onto the tube 12. These are balanced withpanels similarly situated on both the east and west sides of the axis.However, as used here the term “balanced” is not strictly limited tohaving the panels arranged in identical fashion on each side of the tube12. Some imbalance can be permitted, depending on mechanical factors. Avertical pier 16 has a footing 18, e.g., formed of poured concrete,serving as a foundation that is supported in the earth. There is a pivoteye 20 at the top of the pier to support the torque tube 12 so that therow of solar panels 14 can be rocked from an east-facing orientation(FIG. 1B) throughout the day to a mid-day, generally flat orientation(FIG. 1A) and to a west-facing orientation (FIG. 1C). In order to effectrocking motion of the array 10, a tracker actuator 22 is mounted ontothe pier 16, and has an extendible rod member 24 that is pinned to thedistal end of a torque arm or lever arm 26. In this configuration, thetorque arm is about fifteen inches from the axis of the torque tube 12to the rod member 24, and the linear actuator 22 has a stroke capacityof about twenty-four inches. The width of the row of solar panels 14 isabout 12 feet. Here, the torque arm 26 is shown as a separate memberattached to the torque tube, and disposed parallel to the plane of thesolar panels 14. However, in some equivalent arrangements, a pipe or barcould be used, situated parallel to the torque tube and carried on oneside of the row of panels 14. As discussed previously, with thepier-connected drive of this arrangement, the tracker arrangement islimited only to a vertical drive arrangement, and a separate driver isrequired for each row of solar panels. The pier 16 has to be of veryheavy construction because it has to bear the weight of the trackerdrive as well as the weight of the panels, and because it must endurebending torques imposed by the pier-mounted drive. The stroke of thetracker drive is necessarily limited, and so the possible length of thetorque arm 26 is likewise limited. This means that the drive force thatthe actuator 22 has to impose must be rather high

An embodiment of this invention is shown in FIGS. 2A to 2C, which show asolar tracker array 30, viewed along its north-south axis, and rockedinto its mid-day orientation (FIG. 2A), an east-looking orientation(FIG. 2B) and a west-looking orientation (FIG. 2C). A row of solarpanels 34 is supported in a balanced manner by a torque tube 32 which isjournalled in a bearing 40 on top of a pier 36. As in FIGS. 1A to 1C,the pier has a footing 38 set into the earth (or equivalent foundation).In this case, a torque arm 46 is disposed vertically (in FIG. 2A), thatis, generally perpendicular to the plane of the solar panels 34, mountedat one end to the torque tube 32. A horizontal tracker driver is formedof a linear actuator 42 having a body portion 43 that is attached to afixed mount 45 set into the earth at some distance from the footing 38for the pier. The actuator 42 has a generally horizontal rod member 44that is pinned to the distal end of the torque arm 46. Because theactuator 42 is spaced from the pier 36, the stroke length of the rodmember 44 can be quite long. Also, the length of the torque arm 46 canbe long, and can be the length of the pier, meeting the end of the rodmember 44 at ground level. If the earth is dug trenched out at thisarea, the length of the torque arm can exceed the height of the pier.The long torque arm reduces the amount of linear force required to rockthe solar panels. Also, because of the extended torque arm 46, theactuator 42 is able to absorb greater torque loads, e.g., due to winds.

Another embodiment of this invention, has a vertical ground-connecteddrive arrangement, and is shown in FIG. 3A to 3C. Here a row 50 of solarpanels 54 is mounted on a torsion tube 52 that is supported in bearingmembers 60 atop one or more piers 56, each pier having a footing 58supported in the earth. A linear actuator 62 has a vertically orientedbody member 63 and a rod member 64 that extends generally upwards to atorque arm 66 that is fixed to the torsion tube 52. The body portion issupported on a mount or footing 65 that is separated from the footingsfor the piers. In some embodiments, however, the actuator can share thesame footing as one or more of the piers, as long as the long throwlever arm or torque arm is achieved. In this case, the length of thetorque arm 66 is considerably larger than the torque arm 26 of the priorart.

An array of rows of solar panels can all be driven by a singlehorizontal linear actuator, and an example of this configuration isillustrated in FIGS. 4A, 4B, and 4C. Here, there are a series of rowarrangements 30 as in FIGS. 2A-2C, all arranged in parallel, with theirrespective torsion tubes 32 disposed in a north-south orientation. Asingle horizontal tracker driver 42 has its rod member 44 connected tothe torque arm 46 of a first one of the row arrangements 30. Ahorizontal tubular link member 68 then joins that torque arm 46 to thenext torque arm 46. In like manner, successive link members 68 aredisposed across the entire group of row arrangements. These link members68 are articulated to the torque arms 46 and to one another asillustrated in FIG. 5. Wires 69 may be run inside the tubular members.Here, a distal end 70 of the torque arm 46 is connected with a pivot pinto eye members 72 at the ends of the link members 68. Of course, inother embodiments, a single rigid elongated member could be employed inplace of a series of articulated link members. In this embodiment, thesingle driver 42 moves all the row arrangements 30 of the array from aneast-facing orientation (FIG. 4B) through a mid-day orientation (FIG.4A) to a west-facing orientation (FIG. 4C). Also, in this arrangement,the driver is shown positioned at the first or easternmost one of therow arrangements 30, but the driver 42 could be positioned with aninterior row or with the row at the other end.

Details of the horizontal driver or linear actuator 42 are shown inFIGS. 6A and 6B. Here the mount 45 for the actuator is secured in apoured concrete footing 74 in the earth 75. The footing can be of 3000psi concrete, about two feet in diameter and about five to six feet indepth, with the soil about it being recompacted. Also shown here are anelectrical conduit 76 bringing power and signal to an electricaldistribution box 77 mounted on the side of the actuator 72. Also shownhere is a protective boot or sleeve 78 that fits over the rod member 44.

The solar panel arrangements of this invention can be installed onuneven terrain as generally illustrated in FIGS. 7 and 8.

In the FIG. 7 arrangement, a plurality of row arrangements 50 of thetype with vertical drivers (as shown in FIGS. 3A-3C) are each installedin parallel. In this arrangement, each of the rows can be selectivelyprogrammed for respective degrees of tilt in the early morning and lateafternoon so as to create a minimum of shadow on the next adjacent rowof solar panels, as they may be at different altitudes. Here, the piers56, panels 54, and actuators 62 are as generally described earlier.

In the FIG. 8 arrangement, a series of row arrangements 30 of the typehaving a horizontal driver are employed, e.g., as shown in FIGS. 2A-2Cand 4A-4C. The piers 36, panels 44, torque arms 56, and the actuator 42are as generally described before. The articulated linkage mechanism,formed of the series of articulated rigid link members 68, accommodatesdifferences in elevation, as shown, yet achieves accurate tracking.

Several configurations of a large solar array according to thisinvention are shown in plan in FIGS. 9A, 9B, and 9C, with theunderstanding that these are only some of many possible configurations.A generally standard configuration of a solar array 80 is shown in FIG.9A, where there are eight rows 30 of solar panels arranged in parallel.Each row has two wings of equal size, one north of the actuator 42 andlinkage mechanism 68, and the other to the south of them. This is shownin elevation in FIG. 10, where each row 30 has its torsion tube 32supported on a number of spaced piers 36, and with the driver actuator42 situated at a central position between two of the piers. The torquearms 46 are affixed onto the torsion tubes 32 at this position.

As shown in FIG. 9B, a solar array 82 can include one or several rows30′ that are somewhat shortened in respect to the others in order toaccommodate an obstruction 83, which may be a building, a rockoutcropping, or other feature. Alternatively, depending on the sitedimensions, a solar array 84 as shown in FIG. 9C can have a largernumber of rows 30″, which in this embodiment each have a smaller numberof solar panels. Other configurations are also possible. For example,the rows can each have more solar panels to one side or the other of theposition of the driver and linkage mechanism.

The coupling arrangement of torque tube sections according to thisinvention and the bearing design for supporting the torque tube on thepiers are also novel.

Conventional tracker arrangements of the type described here generallyutilize square steel tubes as beams spanning between piers, and this isregarded as optimum for carrying wind-generated torsion to the drivemechanism. The torque tube sections for adjacent spans are typicallyjoined together at the piers, usually by insertion of their ends into alarger square tubular sleeve. This is often a part of the bearing andhas to endure the rotational friction where the torque tubes arejournalled. A disadvantage of the use of these steel sleeves in bearingsis that they have to accommodate both rotary motion and also slidingmotion resulting from thermal expansion of the equipment. The steelsleeve is in moving contact with the pier weldment. Over time, thesteel-on-steel sliding contact will destroy corrosion-protectivefinishes, and will eventually erode the structural steel load-bearingmaterial.

As shown in FIGS. 11 and 12, the bearing arrangement according to thisinvention has a bearing eye 40 which may be welded to the top of thepier 36. Here there is a generally cylindrical outer portion 90. Atubular stub 94 is welded to the cylindrical portion 90 and is mated tothe pier 36. The square torque tube 32 is supported for rotation insidethe cylindrical portion, by means of four plastic bearing inserts 96.Each bearing insert is disposed against a respective flat side of thetorque tube 32, and each insert has a flat side facing the torsion tube32 and a generally rounded side facing the inner wall of the outerbearing portion 90. These inserts 96 can be provided with a notch 98 sothat the inserts may be bound to the torsion tube with tension bands 92.Alternatively, the inserts may be attached with screws or other means.Preferably, the plastic inserts 96 are formed of a durable resin such aspolyethylene or polypropylene, with a suitable lubricant filler. A UVprotective additive, such as carbon black, can also be used. Theseinserts can be cut from a flat sheet of material and need not be formedby expensive molding techniques. It should be appreciated that theinserts 96 easily accommodate both rotary motion of the torsion tube andalso linear motion (e.g.; due to thermal expansion).

As also shown in FIG. 13, the torsion tube 32 is formed of successivetube sections 132, 132. Each section 132 has one swaged end 133 and oneunswaged end 134. The swaged tube end 133 fits tightly into the unswagedend 134 of the next adjacent tube section. This eliminates theadditional fabricated square tubular sleeve, and produces a tighterconnection between adjacent torque tube portions. The swaging of thetube ends 133 can be carried out at low cost on line productionequipment.

The term “earth” as used in reference to the foundation for the pierfootings is not limited to soils and natural terrain surfaces. The solarcollectors of this invention can be installed on an artificial surface,such as a building rooftop, or on the upper level of a parking ramp.

FIG. 15 is a simplified side elevational view of a section of torquetube 32 and solar panels 34 of FIG. 2A, shown at a noontime or middayorientation and viewed along an east-west orientation. This figureillustrates the distance y between the center of gravity cg of the solarpanel and the torsion tube axis A. FIG. 16 is a simplified view of theapparatus of FIG. 15 viewed along torsion tube axis A. FIGS. 17 and 18are similar to FIG. 16 with the structure at a relatively low tilt anglein FIG. 17 and a correspondingly small torque arm X₁, and a relativelylarge tilt angle in FIG. 18 with a longer torque arm X₂.

PV modules 34 are attached to the top of torque tube 34 in a way thatminimizes the distance y from the torque tube rotational axis A to thecg of the system, that is the PV modules 34 and any mounting hardware.This was done to minimize the torque that is generated by the deadweight of the system as the system is rotated around torque tube axis A.In FIGS. 17 and 18, it can be seen that that torque is calculated asW*x, while the torque generated by the wind load is WF*e.

The above-described structure illustrated in FIGS. 1-18 is conventional.

FIGS. 19-24 illustrate a first embodiment of the present invention. Thepresent invention differs from that exemplified in FIGS. 1-18 in that PVmodules 34A are mounted on torsion tube 32 at an angle B. By tilting PVmodules 34A and thereby increasing the distance y to the cg, the designtorque for the torque tube greatly increases, particularly at hightorque tube rotation angles, which typically or occur in the morningsand evenings.

It has previously been assumed that because the major design determinantfor the torque tube size and cost is the torque on the torque tube, thatit was essential to minimize both the torque generated by dead weightand the torque generated by wind force. However, through detailedinvestigations and analyses it has been determined that 1) the windtorque is actually highest when the torque tube rotational angle B isrelatively low (for example 10-20 degrees) and lowest when therotational angle is highest (typically 45 degrees); and 2) the dead loadtorque is lowest at relatively low rotational angles and highest at highrotational angles. Therefore, increase in y distance to the cg of thetilted PV modules 34A of FIGS. 19-24 does not lead to a significantincrease in the design maximum torque delivered to the torque tube.Based upon this quite unexpected result, it has been determined that thesize and cost of the torque tube does not increase significantly for thetilted (FIGS. 19-22) vs. horizontal (FIGS. 1-18) configurations.

FIGS. 23 and 24 show one method for attaching PV modules 34A at a tiltangle B to torque tube 32. A mounting structure 150 comprises a pair ofmounting plates 152, 154. Each mounting plate includes a generallytriangular torsion tube portion 156 and an elongated, generallyrectangular solar panel portion 158 extending at a right angle fromtorsion tube portion 156. Mounting plates 152, 154 are typicallysheetmetal components bent and punched, with bolts engaging holes andclamping the mounting plates to opposite sides of torque tube 32.Attachment could also be by, for example, welding or the use ofbrackets. PV modules 34 are bolted or riveted or otherwise secured tomounting structure 150 in a conventional fashion.

FIGS. 25-31 are directed to a further embodiment of the invention. FIG.25 is a downwardly and North-facing view of the ends of two rows oftracking solar collection assemblies 200 of a tracking solar collectorinstallation 201. Each assembly 200 includes a series of tracking solarcollectors 202. Each tracking solar collector 202 includes a PV modulearray 204 (see FIG. 27) with the PV module array of each tracking solarcollector at a no-tilt, noontime orientation. Each assembly 200 alsocomprises a tilting assembly 206 constructed to tilt each PV modulearray 204 in the same row of assemblies 200 between an East-tiltingorientation, through a no-tilt orientation, shown in FIG. 25, and aWest-tilting orientation shown in FIG. 26. Assemblies 200 are designedto permit tilting to about 45° from horizontal. It should be noted thatPV module arrays 204 are generally rectangular, as opposed to thewedge-shaped arrays in many conventional tilting solar collectorassemblies. See, for example, U.S. Pat. No. 6,563,040. It has been foundthat the wedge-shaped arrays, (placed on sites at the same density aswith rectangular arrays), at the extreme tilting angles used in earlymorning and late afternoon, tend to shade adjacent PV arrays; tocounteract this shading, the tilt angle is commonly reduced, called backtracking. While back tracking reduces shading, it causes the PV modulearray to be at less than an optimal tilt angle thus reducing efficiency.It has been found that by ensuring that the lower ends of PV modulearrays 204 are at a sufficient height above the support surface 208 sothat proper tilting is not prevented by the arrays contacting the groundan extreme tilting angles, PV module array 204 may be made with parallellateral sides, typically in a rectangular configuration, to reduce oreliminate the need for back tracking. Support surface 208 can be, forexample, paved or unpaved soil or other natural surface, a reservoircover, or a roof.

FIGS. 25-31 illustrate the support structure of tracking solarcollectors 202 used to support PV module arrays 204. The supportstructure includes a series of south side supports 212-214 and a seriesof North side supports 216-218. Each south side support 212-214 includesa base 220 extending into support surface 208, a post 222 extendingvertically upwardly from base 220 and a pivot connector 224 at the upperend of post 222. Each North side support 216-218 includes a base 226,one or two struts 228 connected to base 226 by a Y-connector 230 and asecond pivot connector 232 at the upper ends of struts 228. See FIG. 31.

PV module assembly 204 comprises a torque tube 236, a series of a modulerails 238 secured to an extending laterally from each side of torquetube 236 and an array of PV modules 240 mounted to and supported bymodule rails 238. First and second pivot connectors 224, 232 are mountedto torque tube 236 at first and second support points along the torquetube. First and second pivot connectors 224, 232 are constructed topermit torque tube 236 to rotate about its own axis, that is tilt axis237, to permit PV module assembly 204 to be tilted and track the sun.First pivot connector 224 is also constructed to permit torque tube 236and thus PV module assembly 204 to pivot vertically about a pivot 242,shown in FIG. 29. This permit the North-south inclination angle of PVmodule assembly 204 to be easily changed, typically according to thelength of either fixed length or variable length struts 228. Thispivotal feature also permits torque tube 236 and module rails 238 to beoriented horizontally when, for example, PV modules 240 are mounted tomodule rails 238 in the field.

FIGS. 28 and 29 illustrate tilting assembly 206, the tilting assemblyincluding a driver 244 including a drive rod 246 pivotally connected toa drive element coupler 248 at the distal end of drive rod 246. Driveelement coupler 248 is pivotally connected to a series of drive elements250. Each drive element 250 is non-rotatably secured to the torque tube236 of the corresponding PV module assembly 204. Therefore, actuation ofdriver 244 causes drive rod 246 to push or pull drive element coupler248 causing the entire series of PV module assemblies 204 for that rowof tracking solar collector assemblies 200 to tilt, typically accordingto the position of the sun.

FIG. 29A is a schematic illustration of an alternative to the tiltingassembly of FIG. 29. Pulley-type drive elements 254 are secured to thetorque tubes and are connected to one another by belts, cables or chains256, acting as the drive element coupler. A rotatable driver 258 isconnected to and drives one of the torque tubes, and thus one of thepulley-type drive elements 254. Therefore, rotating driver 258 rotatesthe series of pulley-type drive elements 254 and the torque tubestherewith.

As is evident from the figures, Southside supports 212-214 are generallyvertically aligned with the corresponding tilt axes 237. Posts 222 ofSouthside supports 212-214 are relatively sturdy because they mustwithstand tension and compression forces as well as bending moments. Byplacing the base 226 of North side supports 216-218 centrally betweeneach torque tube 236, by securing each torque tube 236 to two downwardlyangled struts 228 and by keeping the height of Y-connector 230relatively short, the forces exerted by PV module arrays 204 on Northside supports 216, 218 are controlled. That is, the bending moments onY-connectors 230 are reduced by minimizing their heights. The use of twodownwardly angled struts 228 connected to each torque tube 236 with thestruts extending from positions laterally offset from the torque tubessubstantially eliminates bending moments on the struts so the struts areprimarily in tension or compression. In the preferred embodiment base226 of the North side supports typically includes a galvanized steel, 3in. diameter, 4 ft. long schedule 40 pipe (not shown) embedded within a2 ft. diameter by 4 ft. deep concrete filled hole. This can be comparedwith the construction of the Southside supports in which base 220typically includes a galvanized steel, 5 in. diameter, 6 ft. longschedule 40 pipe (not shown) embedded within a 2 ft. diameter by 6 ft.deep concrete filled hole. It is preferred that the base 226 of theNorth side supports be located laterally midway between the torque tubesto which they are connected.

The preferred embodiment the north-south inclination of tilt axis 237 isabout 20°. The range of north-south inclinations is preferably about15°-30°. Each PV module array 204 typically comprises 18 PV modules 240.Each tilting assembly 206 typically is designed to operate 24 trackingsolar collectors 202. Tracking solar collector assemblies 200 providegood access around the structures for maintenance. When assemblies 200are mounted to a support surface 208 that requires mowing or access bygrazing animals, the open design of the components of assemblies 200permits the necessary access.

Struts 228 are preferably perpendicular to torque tube 236. See FIG. 27.Therefore if PV module assembly 204 is tilted until it is, for example,parallel to or past one of the struts 228, about 45° in the disclosedembodiment, struts 228 will have the ability to pass into the gap 241between two rows of PV modules 240. The combination of the perpendicularorientation of struts 228 and torque tube 236 and the provision of aproperly sized gap 241 helps to expand the range of available tiltangles for PV module assembly 204 while helping to prevent damage toassemblies 204 caused by over-rotation of assemblies 204.

It is generally preferred that at the maximum rotation of PV moduleassembly 204, struts 228 only approach assembly 204 but do not touch theassembly. Is not desirable to have struts 228 located above PV modules240 because the struts will shade the PV modules. Because the width ofthe shadow created by the strut at such extreme inclination angles islarge relative to the size of PV modules 240, any significant shading ofthe PV modules will reduce and may effectively stop the energyproduction of the array.

If struts 228 were replaced with very narrow support members, so thatthe width of struts 228 is very small in relation to the size of PVmodules 240, the struts could shade the PV modules without significantlylimiting the performance of the array. This would be the case if struts228 were replaced by, for example, cables. FIG. 32 is a simplifiedSouth-facing view of an alternative to the North side supports of FIGS.25-31. North side supports 260-265 replace struts 228 with cables 268,269 and a generally vertical post 270. Cables 268, 269 and post 270 arepreferably oriented perpendicular to torque tube 236 and thusperpendicular to tilt axis 237. Post 270 preferably lies verticallybeneath tilt axis 237. Cables 268, 269 act as opposing tension struts(one will be under tension while the other can be slack under wind load)while posts 270 act as compression struts. In this way the number ofcompression members of the embodiment of FIGS. 25-31 (struts 228) isreduced by 50%, with one of the compression members replaced by a pairof tension members (cables 268, 269) for interior North side supports262, 263. As shown in the FIG. 32, the end-most North side supports 260,265 do not need posts 270; North side supports 260, 261 do not needcables 269; and North side supports 264, 265 do not need cables 268.With this arrangement PV module arrays 204 may be routinely rotatedabout tilt axis 237 so that cables 268, 269 are above PV modules 240 ofPV module arrays 204 without causing unacceptable shading of PV modules240. It is expected that such positioning of cables 268, 269 above PVmodules 240 will occur routinely because of the attachment geometry ofcables 268, 269. With the cable strut embodiment of FIG. 32, anyinaccuracy in the pier placement in the field for base 226 can beaccommodated because the length of cables 268, 269 can be adjusted basedon the as-built pier layout.

FIG. 33 illustrates an alternative to the embodiment of FIG. 32. Theembodiments are very similar with the exception that cables 274, 276 and278 replace cables 268 and 269. The FIG. 33 embodiment is somewhatsimpler in construction than the FIG. 32 embodiment. Cables 276 connectthe upper ends of posts 270 to one another, preferably at or near secondpivot connectors 232. Cables 274, 278 secure the end-most posts 270 tothe ground or other support surface. Cables 274, 276 and 278 aresufficiently thin so that when PV module arrays 204 are in a tiltedorientation, as illustrated in dashed lines in FIG. 33, the cables donot significantly shade the PV module arrays. Cables 276, when thesystem is under wind load, will typically be in tension with one ofcables 274, 278 being in tension and the other being slack.

It is generally preferred that cables 268, 269, 274, 276 and 278 extendfrom positions at or near the second pivot connectors 232 at the end ofposts 270. However, in some cases it may be desirable to offset some orall of the cables from second pivot connectors 232. In such cases thegap 241 of between the PV modules 240 will preferably be aligned withthe attachment points of the cables rather than at or near second pivotconnectors 232.

Modification and variation can be made to disclose embodiments withoutdeparting from the subject of the invention. For example, struts 228could be made to be variable length struts to permit the north-southinclination angle of PV module assemblies 204 to be adjusted. Torquetube 36 may have a variety of cross-sectional shapes, may have apartially or fully solid interior, may be made of one or more materials,and may have its various structural features vary along its length.Torque tube 236 and module rails 238, which act as a support or framefor PV modules 240, could be replaced by other solar collector supportstructure, such as a rigid rectangular platform. Therefore, tiltingassembly 206 could be secured to structure other than torque tube 236.The solar collector support structure could be mounted so to tilt notabout a fixed tilt axis 237 but, for example, about a range ofinstantaneous tilt axes. For example, the solar collector supportstructure could be supported on a curved surface so that actuation oftilting assembly 206 causes the solar collector support structure toroll over the curved surface. In such a case, the average or medianother representative tilt axis can be considered to be the tilt axis.

Any and all patents, patent applications and printed publicationsreferred to above are incorporated by reference.

1. A tracking solar collector assembly comprising: first and secondtracking solar collectors; first and second Southside supports; first,second and third North side supports; the Southside supports and theNorth side supports defining first and second generally parallel paths,the first and second paths being generally East-West paths, the firstand second paths being spaced apart from one another; the first trackingsolar collector comprising first solar collector support structure; thesecond tracking solar collector comprising second solar collectorsupport structure; the first and second solar collector supportstructures each having first and second spaced apart pivotal supportpoints defining a tilt axis; at least one solar collector mounted toeach solar collector support structure; the first support points of thefirst and second solar collector support structures pivotally connectedto and supported by the first and second Southside supports,respectively; the second support point of the first solar collectorsupport structure pivotally connected to and supported by the first andsecond North side supports; the second support point of the second solarcollector support structure pivotally connected to and supported by thesecond and third North side supports; and a tilting assembly comprising:a drive element secured to each solar collector support structure; adrive element coupler operably coupling the drive elements, the driveelements and the drive element coupler creating a drive assembly; and adriver coupled to the drive assembly so that operation of the drivercauses the drive elements move in unison thus causing the solarcollector support structures and the solar collectors therewith to tiltin unison.
 2. The assembly according to claim 1 wherein at least onetilt axis is at an angle to a horizontal line.
 3. The assembly accordingto claim 2 wherein said angle is between about 15° to 30° .
 4. Theassembly according to claim 2 wherein said support element is avariable-length support element to permit said angle to be changed. 5.The assembly according to claim 1 wherein the drive element is securedto each solar collector support structure at a point between the firstand second support points.
 6. The assembly according to claim 1 whereina plurality of said solar collectors are mounted to the solar collectorsupport structures.
 7. The assembly according to claim 6 wherein thesolar collectors define an array of solar collectors having generallyparallel lateral sides.
 8. The assembly according to claim 1 wherein thesolar collector comprises a PV module.
 9. The assembly according toclaim 1 wherein the first and second Southside supports are generallyvertically aligned with the tilt axes of the first and second solarcollector support structures, respectively.
 10. The assembly accordingto claim 1 wherein the second North side support is positioned laterallybetween the tilt axes of the first and second solar collector supportstructures.
 11. The assembly according to claim 1 wherein the secondNorth side support is positioned laterally midway between the tilt axesof the first and second solar collector support structures.
 12. Theassembly according to claim 1 wherein the first, second and third Northside supports each include a base securable to a support surface, eachbase laterally offset from the tilt axes of the first and second solarcollector support structures.
 13. The assembly according to claim 12wherein the base of the second North side support is positioned at aposition laterally midway between the tilt axes of the first and secondsolar collector support structures.
 14. The assembly according to claim1 wherein each North side support comprises a base, mountable to asupport surface, and at least one support element connecting the base toa second support point.
 15. The assembly according to claim 14 whereinthe base of the second North side support is positioned generallyequidistant from the second support points of the first and second solarcollector support structures.
 16. The assembly according to claim 14wherein said support element is a fixed-length support element.
 17. Theassembly according to claim 1 further comprising a fourth North sidesupport, and wherein: the second support point of the first solarcollector support structure is pivotally connected to and supported bythe first, second and third North side supports; and the second supportpoint of the second solar collector support structure is pivotallyconnected to and supported by the second, third and fourth North sidesupports.
 18. The assembly according to claim 17 wherein the secondsupport point of the first solar collector support structure isconnected to the first and third North side supports by tension strutsand to the second North side support by a compression strut.
 19. Theassembly according to claim 18 said wherein the tension struts comprisecables and the compression strut comprises a post.
 20. The assemblyaccording to claim 18 wherein the compression strut is verticallyaligned with the tilt axis of the first solar collector supportstructure.
 21. The assembly according to claim 1 wherein the solarcollector support structure comprises a torque tube extending along thetilt axis.
 22. The assembly according to claim 21 wherein the solarcollector support structure comprises module rails secured to the torquetube and extending laterally from the torque tube.
 23. A tracking solarcollector installation comprising a tracking solar collector assemblyaccording to claim 1 mounted to a support surface.
 24. The installationaccording to claim 23 wherein the support surface comprises the ground.25. The installation according to claim 24 wherein the ground isunpaved.
 26. The installation according to claim 23 wherein the supportsurface comprises a roof.
 27. The installation according to claim 23wherein the support surface comprises a reservoir cover.
 28. Theassembly according to claim 1 wherein a plurality of solar collectorsare mounted to the solar collector support structures, said plurality ofsolar collectors defining a gap between the solar collectors, the gapextending perpendicular to the tilt axis.
 29. The assembly according toclaim 28 wherein at least one of the North side supports compriseslaterally extending support elements extending generally perpendicularto the tilt axes and aligned with the gap so that tilting the solarcollector support structures and the solar collectors therewith causesthe laterally extending support elements to pass through the gap. 30.The assembly according to claim 29 wherein the laterally extendingsupport elements comprise struts.
 31. The assembly according to claim 30wherein the struts comprise flexible cables.
 32. The assembly accordingto claim 30 wherein the struts comprise rods.